Burnishing box tools



Dec.

s. N. FAWELL 3,115,704

BURNISHING BOX TOOLS Filed Jan. 9, 1962 INVENTOR STANLEY N. FAWELL.

ATTORNEYS 3,115,704 BURNISHHNG BOX T0015 Stanley Nathan Fawell, llford,Essex, England, assignnr to Fletcher, Brock dz Collis, Ltd, Hainanlt,England, a company of Great Britain Filed Jan. 9, 1962, Ser. No. 165,087Claims priority, application Great Britain Jan. 12, 1961 4 (llairns.(Cl. 29-566) This invention relates to burnishing box tools suitable foruse in automatic machine tools, being box tools (i.e. tools adapted tobe applied to a relatively rotating workpiece held by one end over thefree end thereof) having a cutting bit and burnishing members. Such atool will be referred to herein as a tool of the kind specified.

Tools of the kind specified are used for providing the workpiece, forexample the shank of a bolt, with a smoothed, burnished, cylindricalsurface. The tool is applied over a free end of the relatively rotatingworkpiece and is advanced along the workpiece towards the chuck orcollet which holds it, during which movement the bit removes surplusmaterial and forms a cylindrical surface while the burnishing members(usually hardened steel wheels) smooth out the marks made by the bit andproyide a burnished surface.

One problem which is encountered with such tools is the removal of thetool from the workpiece. If the bit is not retracted from the workpieceit may score the workpiece as the tool is withdrawn. Also, the tip ofthe bit sometimes tends to dig into the workpiece when it comes upagainst a shoulder at the end of the cylindrical surface, e.g. thelunderside of the head, in the case of a bolt. If the bit isnon-retractable, withdrawal of the tool is difiicult in suchcircumstances. Various types of openable box tools have been devised inattempts to solve these problems, but these have the disadvantages thatthey must be opened and re-closed by the machine operator, or are verycomplicated.

It is an object of the invention to provide a bu-rnishing box tool ofthe kind specified which opens automatically upon withdrawal of theworkpiece and which is of relatively simple construction.

According to the present invention, in a burnishing box tool of the kindspecified the bit is mounted on a carrier which is capable of limitedmovement relative to the body of the tool between an advanced positionin which the tip of the bit is at its nearest to the axis of theworkpiece and farthest from the front of the tool and a retractedposition in which the tip of the bit is at its farthest from the axis ofthe workpiece and nearest to the front of the tool.

Thus, as the tool is applied to the workpiece the reaction on the bitforces it rearwardly with respect to the body of the tool and inwardlytowards the axis of the workpiece, whereas when the tool is beingwithdrawn the reaction on the bit forces it forwardly with respect tothe body of the tool and outwardly away from the axis of the workpiece.

If desired, the bit carrier may be spring-biased towards its retractedposition.

In one form of the invention the bit carrier is pivoted to the body' ofthe tool about an axis lying in a transverse plane perpendicular to theaxis of the workpiece and to the rear of the parallel transverse planecontaining the tip of the bit, whereby the reaction on the bit when thetool is applied to the workpiece tilts the bit carrier towards theworkpiece, whereas the opposite reaction when the tool is beingwithdrawn tilts the bit carrier away from the workpiece.

The range of movement of the bit carrier can be very small, e.g. only athousandth of an inch or so at the tip 3,1157% Patented Dec. 31, 1963ice of the bit. A suitable adjustable stop, or adjustable stops, may beprovided for determining the limiting positions.

The bit may be adjustably clamped in a slide way in the bit carrier sothat its position can be adjusted.

The invention may be performed in various ways and a specific embodimentwill now be described by way of example with reference to theaccompanying drawings, in which:

FIGURE 1 is a side elevation of a simplified form of box tool embodyingthe invention, diagrammatically exaggerated to show the principle ofoperation;

FIGURE 2 is a side elevation of a practical embodimerit;

FlGURE 3 is an end view looking from the right in FIGURE 2;

FIGURE 4 is an end view looking from the left in FIGURE 2, the toolhaving been rotated anti-clockwise through from the position in which itis shown in FIGURE 2; and

FIGURE 5 is a section taken on the line VV in FIGURE 4.

Referring to FIGURE 1, the box tool indicated generally by the referencenumeral 10 comprises a body 11 having fixed thereto a shank 1 2 by whichthe tool can be mounted in a machine such as a lathe, e.g. in a colletmounted in the 'tailstock. The box tool 1t is adapted to machine acylindrical surface on a workpiece 13 by means of a cutting bit 14, andto b-urnish the machined surface by means of at least one burnishingroll 15, as the workpiece 13 is rotated relatively to the box tool aboutan axis 16 and advanced in the direction of the arrow 17. The workpieceaxis 16 is coincident with the axis of the shank 12. The body 11 has awell 18 into which the tip of the workpiece 13 can enter.

The burnishing roll 15 is mounted on an axle 19 in a support member 20clamped to the body 11. The support member can be adjusted relative tothe axis 16 in :order that the box tool can accommodate workpieces ofdifferent diameters.

The cutting bit 14 is mounted in a bit carrier 21 which is p-ivotallyconnected to the body 10 by a pivot pin 22. The axis of the pivot pin 22lies in a transverse plane indicated by the chain line 23, which planeis perpendicular to the axis 16. The cutting tip of the tool 14 lies inanother transverse plane 24 which is parallel to the plane 23. The plane23 lies to the rear of the plane 24 by a distance a. For clarity, inFIGURE 1 the distance a is much exaggerated. The expressions front andrear as used herein designate respectively the parts of the box toolthat are nearest to, and farthest from, the tip of the workpiece 13 atthe beginning of its advance into the tool.

A stop formation 25 on the body 10 limits the extent of clockwiserotation of the bit carrier 21 and hence defines the closest limitingposition of the bit 14 to the axis 16-.

In operation, as the workpiece is advanced in the direction of the arrow17, a torque is exerted upon the bit carrier 21 tending to turn it inthe clockwise direction in FIGURE 1 and so hold it against the stopformation 25. On the other hand, when the workpiece is withdrawn in theopposite direction to the arrow 17 the drag on the bit 14 will tend toturn the carrier slightly in the anticlockwise direction so that the tipof the tool 14 will move for a short distance in the direction of thearrow 26 along an are 27, the centre of which is the pivot pin 22. Sincethe plane 23 of the pivot pin 22 is to the rear of the plane 24 of thetip of the bit, any movement of the tip of the bit 14 along the are 27in the direction of the arrow 26 will increase the radial distance fromthe axis 16 to the tip of the bit, i.e. the tool will open slightly andpermit free withdrawal of the workpiece =13.

If the bit 14 engaged the workpiece 13 at the side, i.e. in a horizontalplane containing the axis 16 as shown in dotted lines, the samerelieving effect would occur on withdrawing the workpiece, since theupward movement of the bit resulting from anti-clockwise movement of thebit carrier '21 would swing the tip of the bit upwardly in a verticalplane tangential .to the side of the workpiece. Indeed, a relievingeflect Will occur upon withdrawal of the workpiece wherever the bitengages it, provided the point of contact is not below a horizontalplane containing the axis 16.

In FIGURES 2 to 5 parts which correspond to those shown diagrammaticallyin FIGURE 1 have been given the same reference numerals. In this casethere are two burnishing rolls and 15 which have separate carriers and Nboth of which are adjustable radially in slots and 30 (FIGURE 3) andwhich can be locked in the desired position of adjustment by clampingbolts 31 and 31 The bit carrier 21 is provided with a groove 32 whichaccommodates the bit 14 (FIGURE 4), which is clamped between an arcuatepad 33 in one wall of the groove 32 and screws 34 which pass through theopposite wall of the groove 32. The bit carrier 21 has a lug portion 35which is accommodated in a slot of corresponding width in the body 10and which is bored to receive the pivot pin 22.

In this practical embodiment the range of movement of the bit carrier 21is very small; a thousandth of an inch or so of movement at the tip ofthe bit is sufficient. The limits of this range of movement aredetermined by two stops. One of these stops is constituted by a screw 35(FIGURE 5) having a lock nut 37. This screw corresponds to the stopformation 25 shown in FIGURE 1 in that it determines the innermostlimiting position of the bit 14, i.e. it limits the anti-clockwisemotion of the bit carrier 21 in FIGURE 5, about the pivot pin 22. Theother stop limits the outward movement of the bit M by limiting theclockwise movement of the bit carrier 21 in FIGURE 5. This stopcomprises a screw 38 the head 39 of which is accommodated in a recess 40in the body 10. When the carrier 21 is against the first mentioned stopscrew 36, there is a small clearance of about a thousandth of an inch orso between the underside of the head 39 and the base of the recess 40.As the bit carrier 21 moves clockwise in FIGURE 5 upon Withdrawal of theworkpiece to the left, the stop screw 38 moves with it until theunderside of the head 3? comes up against the base of the recess 40. Theextent of this movement can be adjusted by screwing the screw 38 in orout. The stop screw 38 is locked in its adjusted position by means of agrub screw 41.

Surrounding the stop screw 38 is a coil spring 42 which lightly biassesthe bit carrier 21 in the clockwise direction in FIGURE 5. This biassesthe tool towards the open position. The loading of the spring is readilyovercome when a workpiece is introduced into the tool, from the left inFIGURE 5.

What I claim as my invention and desire to secure by Letters Patent is:

1, A burnishing box tool adapted to be applied axially over one end of arelatively rotating workpiece, said box tool comprising a body, at leastone burnishing member, means mounting said burnishing member on saidbody, a bit having a cutting tip, a bit carrier, means fixedly mountingsaid bit in said bit carrier, pivot means mounting said bit carrier onsaid body for pivotal movement about an axis lying in a transverse planeperpendicular to the rotational axis of said work piece and to the rearof a parallel transverse plane containing said cutting tip of said bitand stop means carried by said body and disposed to support said bitcarrier with said cutting tip of said bit in its rearmost position.

2. A burnishing box tool according to claim 1 which has at least oneadjustable stop which determines at least one limit pivotal position ofsaid bit carrier.

3. A burnishing box tool according to claim 1 in which said bit isadjustable relatively to said bit carrier.

4. A burnishing box tool according :to claim 1 and including springmeans biassing said bit carrier towards a limit pivotal position inwhich said cutting tip of said bit is at its farthest from saidrotational axis of said workpiece.

References Cited in the file of this patent UNITED STATES PATENTS427,902 Porteous May 13, 1890 1,056,097 Hartness Mar. 18, 1913 1,085,800Crandall Feb. 3, 1914

1. A BURNISHING BOX TOOL ADAPTED TO BE APPLIED AXIALLY OVER ONE END OF ARELATIVELY ROTATING WORKPIECE, SAID BOX TOOL COMPRISING A BODY, AT LEASTONE BURNISHING MEMBER, MEANS MOUNTING SAID BURNISHING MEMBER ON SAIDBODY, A BIT HAVING A CUTTING TIP, A BIT CARRIER, MEANS FIXEDLY MOUNTINGSAID BIT IN SAID BIT CARRIER, PIVOT MEANS MOUNTING SAID BIT CARRIER ONSAID BODY FOR PIVOTAL MOVEMENT ABOUT AN AXIS LYING IN A TRANSVERSE PLANEPERPENDICULAR TO THE ROTATIONAL AXIS OF SAID WORK PIECE AND TO THE REAROF A PARALLEL TRANSVERSE PLANE CONTAINING SAID CUTTING TIP OF SAID BITAND STOP MEANS CARRIED BY SAID BODY AND DISPOSED TO SUPPORT SAID BITCARRIER WITH SAID CUTTING TIP OF SAID BIT IN ITS REARMOST POSITION.